COPYSIGN(3)                Linux Programmer's Manual               COPYSIGN(3)



NAME
       copysign, copysignf, copysignl - copy sign of a number

SYNOPSIS
       #include <math.h>

       double copysign(double x, double y);
       float copysignf(float x, float y);
       long double copysignl(long double x, long double y);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       copysign(), copysignf(), copysignl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION
       These  functions return a value whose absolute value matches that of x,
       but whose sign bit matches that of y.

       For example, copysign(42.0, -1.0) and copysign(-42.0, -1.0) both return
       -42.0.

RETURN VALUE
       On  success,  these  functions  return a value whose magnitude is taken
       from x and whose sign is taken from y.

       If x is a NaN, a NaN with the sign bit of y is returned.

ERRORS
       No errors occur.

ATTRIBUTES
       For  an  explanation  of  the  terms  used   in   this   section,   see
       attributes(7).

       allbox;  lbw36  lb  lb l l l.  Interface Attribute Value T{ copysign(),
       copysignf(), copysignl() T}   Thread safety  MT-Safe

CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.  This function is defined in  IEC  559
       (and the appendix with recommended functions in IEEE 754/IEEE 854).

NOTES
       On architectures where the floating-point formats are not IEEE 754 com-
       pliant, these functions may treat a negative zero as positive.

SEE ALSO
       signbit(3)

COLOPHON
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       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.



GNU                               2017-09-15                       COPYSIGN(3)